I actually found this out by accident. AFAIK, this only works if your car has Bluetooth. I paired my phone with my car - Honda Accord - [right now it's iPhone 5 but I can't see why it wouldn't also work with Android]. Switched over to the Bluetooth source in the car so as to hear the music on my phone in the ipod music section on the car's stereo speakers. Plus set my navigation program. I was going somewhere that I knew how to go but I wanted to make sure that it was working OK. Lo and behold, when I got to a point in the nav when an audio announcement was made, the ipod music sound level decreased and the nav audio voice played through the car's speakers. Nice!